Chromosome abnormalities in 447 couples undergoing intracytoplasmic sperm injection--prevalence, types, sex distribution and reproductive relevance.

Chromosomal abnormalities are thought to be a major contributor to the genetic risks of infertility treatment by intracytoplasmic sperm injection (ICSI). Apart from abnormalities arising de novo, abnormal karyotypes in pregnancies conceived through assisted reproductive technology may be directly derived from predisposing parental aberrations. In a prospective study we have analysed the chromosomes of 868 male and female patients prior to planned ICSI treatment. A total of 33 aberrant karyotypes was diagnosed, corresponding to an abnormality rate of 7.6% per couple or 3.8% per individual studied. Even though male factor infertility was twice as common as female factor infertility in this cohort, 24 of the chromosomal abnormalities were found among the women. Low-level mosaicism for numerical sex chromosome anomalies was diagnosed in 20 individuals, and one patient had the triple X karyotype. With respect to structural chromosomal anomalies, we found six reciprocal and three Robertsonian translocations, two paracentric inversions and one marker chromosome. Many of the aberrations that we diagnosed could be classified as carrying only a small to moderate reproductive risk. Given the high rate of abnormal karyotypes among the female subjects, we suggest that not only the males, but both partners should be routinely karyotyped prior to ICSI.